I have new classes, pages, etc in the my Salesforce org. Is it possible to update the project with all new files?
You can use source:retrieve command.
Some of them are like:
To refresh and retrieve the files already pulled in source:
sfdx force:source:retrieve -p path/to/source
To retrieve all Apex classes:
sfdx force:source:retrieve -m ApexClass
To retrieve all custom objects and Apex classes:
sfdx force:source:retrieve -m CustomObject,ApexClass
There are many other commands which you can find in documentation from link above